金属凝固细晶技术及发展

介绍了凝固过程控制在材料加工技术中的地位,阐述了凝固过程的研究内容和凝固组织细化的作用,并对金属凝固组织细化技术中的浇注过程和传热条件控制方法、化学处理方法、机械处理方法以及外加物理场方法作了简单评述;认为温度扰动、成分扰动、外加超声波、脉冲电流或脉冲磁场不仅能有效地细化金属凝固组织,还可以避免其他细化方法对环境和金属材料本身的污染,有利于材料的循环利用.     

高铬铸铁过流冷却过程中初生相的细化球化

采用过流冷却法制备高铬铸铁半固态浆料,对初生相细化球化机理进行研究。结果表明,在冷却体作用下,熔体中大量快速形核长大的初生相通过物理、冶金作用分解和熟化成细小的等轴状颗粒而达到细化球化。树枝状初生奥氏体通过枝晶臂熔断和主干弯曲折断而细化球化,早期以枝晶臂熔断为主,后期以主干在剪切力作用下弯曲折断为主;高硬度的M7C3型初生碳化物通过横向折断和纵向分裂而达到细化球化,早期以横向折断为主,后期以纵向分裂为主。     

Influence of a liquid structural change on the solidification of the alloy CuSn30

The effect of a liquid structural change on the solidification of the alloy CuSn30 is discussed. The temperature dependence of the electrical resistivity (ρ-T) of a CuSn30 (wt.%) melt was measured, and an abnormal change was found on the ρ-T curve within a range of 855°C to 1040°C, which suggests that the melt may have undergone a temperature-induced liquid-liquid structural transition (TI-LLST). The existence of the TI-LLST was verified by means of differential scanning calorimetry. Furthermore, the melt that experienced the TI-LLST needed higher undercooling to nucleate, and the eventual grain size was evidently refined. Analysis of the atomic bonding mechanism of the CuSn30 melt at temperatures above melting point suggest that the structural transition can be attributed to the destruction of the inherited chemical short-range orders or clusters, and that this destruction alone results in the homogeneity of the melt. In turn, the homogeneity of the melt inhibits the nucleation and growth of the primary phase, promotes a peritectic reaction, and eventually refines the solidification microstructures.     

Microstructure and properties of ZL205 alloy

The microstructure, precipitate type, precipitate distribution and tensile strength of a ZL205 alloy, before and after ageing treatment, have been studied by means of optical microscopy and transmission electron microscopy. The results showed that the as-cast microstructure of the alloy was made up of α-Al and eutectic phase distributed at the grain boundaries. During ageing treatment, the tensile strength increased at first and then reduced with time, and the highest ultimate tensile strength was found to be around 488.2 MPa.     

熔体温度处理对Al-25%Si合金显微组织的影响

研究了熔体温度处理工艺对Ａｌ－２５％Ｓｉ合金显微组织的影响。结果发现：熔体温度处理可使Ａｌ２５％Ｓｉ合金初生硅的尺寸大大减小,初生硅尺寸可由处理前的１００μｍ左右减小剂处理后的１５μｍ左右;Ａｌ－２５％Ｓｉ合金熔体温度处理的效果主要受低温和高温熔体温度的影响。     

基于自适应窗的立体相机视差图优化方法研究

针对通过立体匹配直接得到视差图存在空洞等失真点(区域)的问题,本文提出一种基于自适应窗的视差优化方法.该方法先通过左右图像的视差一致性,检测出非零视差失真和黑洞失真区域,然后将所在像素点与周围像素点作视差代价比较,并针对由环境、光照以及其他噪声因素造成的误匹配所导致的黑洞区域,通过采用自适应窗填充黑洞失真区域,进而利用...     

浅度磺化抽余油开发抗磨液压油

以新疆原油减压二、三线去蜡油为原料经浅度磺化、碱洗以及白土精制后得到浅度磺化抽余油 ,其性能符合透平油质量要求 ,调合抗磨液压油质量合格     

Superplasticity in fine-grained AZ61 magnesium alloy

The effect of grain refinement on the superplasticity of ingot-processed magnesium alloy was investigated. From the AZ61 material with a linear intercept grain size of 5 μrn, which was obtained by the multi-rolling process at an elevated temperature, tensile elongation over 400% could be achieved at 10^-3s^-1 at 400°C with a maximum value of 560% at 2x10^-4s^-1 at the same temperature. It was found that grain boundary diffusion controlled grain boundary sliding and pipe diffusion controlled slip creep govern the plastic flow at low and high strain rate ranges, respectively. A deformation map for pure magnesium was constructed to examine the effect of grain size and flow stress on deformation behavior at elevated temperature. The superplastic formability of Mg alloys was demonstrated by forming an AZ61 sheet into a hemi-sphere.     

Al-Ti-B和Al-5%Sr中间合金对轮毂铝合金的晶粒细化和变质作用

采用不同处理状态的Al Ti B中间合金和Al 5 %Sr中间合金 ,对轮毂铝合金Al 7%Si 0 35 %Mg进行晶粒细化和变质处理。在Instron 85 0 2 - 3411型液压伺服疲劳试验机上测试被处理合金的抗拉强度和伸长率。结果表明 :Al Ti B中间合金可有效地细化Al 7%Si 0 35 %Mg合金 ,加入 0 0 6 %Ti即可使合金获得良好的细化效果 ;Al 5 %Sr中间合金可有效地对Al 7%Si 0 35 %Mg合金进行变质 ,加入 0 0 2 %Sr即可使合金获得良好的变质效果 ;快速凝固和热变形处理可有效地改善Al Ti B的晶粒细化效果和Al 5 %Sr的变质效果 ,在获得相同的晶粒细化和变质程度的情况下 ,使Al Ti B和Al 5 %Sr中间合金的加入量减少约 5 0 % ,并使Al 7%Si 0 35 %Mg合金的力学性能有所提高     

GRAIN REFINEMENT OF MICROALLYED STEEL THROUGH HEAVY HOT DEFORMATION AND CONTROLLED COOLING

1.IntroductionAsfinegrainedsteelsshowmanyfaVowhlemechanicalpropertiessuchassbength,ductility,impactproperty,etc,grainrefinementhasbeenanimportantitemamongresearchstudies.Niohitunisveryoftenaddedtoimprovestrengthandlow--temperaturetoughnessOfTMCPsteelsbyinhibitingausteniterecrystallizationandgrain~dabingthermomechAncaltreatment.ItisgenerallybelievedthatthehanimtunferritegrainsizeofcommercialTMCPsteelsrangesfrom3to5Urn['--3),butithasbeenrePOrtedthatthefenitegrainsizecanbereducedto1--ZUmusi…